B04

This project targets a detailed understanding of the multireference electronic structures of FeN4 centers and the effect that magnetic coupling as a subtle energetic perturbation has on their wave functions. Thereby, a fundamental understanding of differences between pyridinic and pyrrolic N-donors is envisaged, and a conceptual framework for treating and analysing magnetically coupled systems with deviations from the Heisenberg energy ladder will be developed. Density matrix renormalisation group (DMRG) calculations and electronic structure analyses based on entanglement measures and spin Hamiltonian parameters will be employed, enabling a direct connection with magnetic and spectroscopic measurements on iron complexes.